Nitrogen, boron-doped Ti3C2 MXene quantum dot-based ratiometric fluorescence sensing platform for point-of-care testing of tetracycline using an enhanced antenna effect by Eu3+

The Ti3C2 MXene quantum dots (Ti3C2 MQDs) derived from Ti3C2 MXene have received much attention because of their remarkable advantages in biosensing. Nevertheless, the functionalization of Ti3C2 MQDs to improve their properties is just in its infant stage. Herein, we firstly synthesized nitrogen and boron co-doped Ti3C2 MQDs (N, B-Ti3C2 MQDs) with good water solubility, strong stability, and high optical characteristics. The N, B-Ti3C2 MQDs exhibit excitation wavelength-dependent blue photoluminescence with optimal excitation/emission peaks at 335/439 nm. Nowadays, the development of fast and real-time detection of tetracycline (TC) in animal derived food is very essential. In this work, a novel point-of-care testing (POCT) platform was established based on ratiometric fluorescence method using N, B-Ti3C2 MQDs coupled with Eu3+. Upon addition of TC in the Eu3+/N, B-MQDs system, blue fluorescence emission of N, B-Ti3C2 MQDs was quenched and red fluorescence emission of Eu3+ was enhanced gradually, which was ascribed to the synergistic inner filter effect and antenna effect. Moreover, we prepared test papers with N, B-Ti3C2 MQDs and Eu3+ for TC detection based on the change of fluorescence color, which could be recognized by color recognizer app installed in the smartphone. Therefore, great promise for POCT of TC is given with the merits of simplicity and visible detection possibility. The proposed method demonstrated a low detection limit of 20 nM. Application of the platform for TC quantification in milk samples opened a novel means for the potential use of N, B-Ti3C2 MQDs in food safety.